Electrical problem

[The Welsh Cruiser]

My water pump packed in this morning. I'm no electrical expert but I think I've ruled some things out but there again, I'm still baffled.

 

First I checked the glass fuse in the fuseboard. It looked OK but I changed it anyway. Next I hooked up some bits of wire from an old battery to the water pump. The pump worked. Next I tried to check the fuseboard switch. I didn't really know how to do this but by using dc voltage and continuity on my meter I established that it behaves in the same way as the other switches, so I assume it's OK.

 

The next bit is what baffles me. I removed the wires from the water pump and checked them with my meter on dc volts. If I switch off the switch on the fuseboard there's little or no reading, just varying mv (millivolts perhaps?).  If I move the fuseboard switch to 'on' I get a varying voltage between 2.5 and 3. My leisure battery is more or less fully charged, sitting at around 14.6v with solar going into it. 

 

Does anyone have any idea what might be going on here?

[rusty69]

You have a high resistance between your battery and your meter.

 

Or

 

Your meter has flat batteries /is knackered/on wrong setting. 

[Tony Brooks]

1 minute ago, rusty69 said:

You have a high resistance between your battery and your meter.

 

Or

 

Your meter has flat batteries /is knackered/on wrong setting. 

OR

between your meter batteries (just to avoid confusion) on the negative. I have known a number of times where a busbar screw on the distribution board has worked loose a d given this sort of reading.

[The Welsh Cruiser]

Thanks I checked the meter on the connections for my solar controller before measuring the voltage, the reading matched the reading on my solar meter.

 

So there's high resistance somewhere between the battery and the pump from what you say. What kind of things might result in this?

[rusty69]

1 minute ago, The Welsh Cruiser said:

 

So there's high resistance somewhere between the battery and the pump from what you say. What kind of things might result in this

Loose or dirty connections on switches, fuse holders, batteries, connectors, or bus bar. 

As Tony said above. 

[Chewbacka]

If you have a supply switch on the fuse board to the pump, try briskly switching it on and off a few times.  If that does nothing with the switch off measure the volts across the back of the switch, it should be about 12v.  Then turn on the switch and measure it again, should be about zero.  Is it?

[The Welsh Cruiser]

24 minutes ago, Chewbacka said:

If you have a supply switch on the fuse board to the pump, try briskly switching it on and off a few times.  If that does nothing with the switch off measure the volts across the back of the switch, it should be about 12v.  Then turn on the switch and measure it again, should be about zero.  Is it?

There are half a dozen switches on the fuse board. I tried what you suggested and just so I can try to understand this, I tested them all. All of them showed zero with the switch on, 13.8v with the switch off apart from the switch to the water pump which showed zero both on and off. So it's the switch right? However I'm now even more confused, with the water pump switch on I've just measured the wire that connects to the water pump it's now miraculously gone up to 9.5v!  

[Alan de Enfield]

Check how well secured the 'glass fuse' is in its receptacle.

 

Spawn of the devil - almost as bad as those ceramic 'bullet fuses.

[The Welsh Cruiser]

2 minutes ago, Alan de Enfield said:

Check how well secured the 'glass fuse' is in its receptacle.

 

Spawn of the devil - almost as bad as those ceramic 'bullet fuses.

I've tried 3 different fuses, same result. I'm getting some kind of voltage at the pump, so I don't think it's the fuse.

[matty40s]

Almost maybe the isolator switch, try running the water pump by running a tap and then press /play withthe isolator switch and see if the pump runs sporadically.

[Chewbacka]

Measure the volts on the supply side of the switch relative to battery negative with the switch on and off, what do you get?

[rusty69]

You could temporarily bypass the switch, or borrow one of the other switches, assuming they are the same rating. 

[The Welsh Cruiser]

24 minutes ago, Chewbacka said:

Measure the volts on the supply side of the switch relative to battery negative with the switch on and off, what do you get?

I'm not quite sure but if I say there are no voltage readings from that switch, regardless of what I do or where I measure, does that answer?

22 minutes ago, rusty69 said:

You could temporarily bypass the switch, or borrow one of the other switches, assuming they are the same rating. 

I'd like to use another switch, there's one labelled bilge pump that has wires going to it but isn't used but unfortunately everything's soldered, and I don't have an iron. How might I bypass it?  

[rusty69]

18 minutes ago, The Welsh Cruiser said:

I'm not quite sure but if I say there are no voltage readings from that switch, regardless of what I do or where I measure, does that answer?

I'd like to use another switch, there's one labelled bilge pump that has wires going to it but isn't used but unfortunately everything's soldered, and I don't have an iron. How might I bypass it?  

If you are getting no voltage measurement on either of the cables on the switch relative to you battery negative, there is no point bypassing it (using a suitably sized piece of cable, but not bypassing the fuse if it has one built into the switch). 

 

Trace the cable back from the switch, towards the battery until you measure battery voltage. 

 

How sure are you that the switch you are testing is the pump switch? 

Edited September 28, 2019 by rusty69
Deleted a bit

[Chewbacka]

I am assuming that the circuit is

Battery

Fuse

Switch

Pump

 

If so, if there is no voltage on the supply to the switch, then there is no power getting to the switch.

So can you measure the voltage on the fuse holder with the fuse in place?

 

If so measure between negative and

1) fuse supply

2) fuse output 

 

Added - Do this with the switch on and off

Edited September 28, 2019 by Chewbacka

[The Welsh Cruiser]

I'm not the most experienced with electrics! The switch panel has 6 toggle switches, opposite each is a glass fuse that's held in by a screw cap. To be honest I've no idea what wires feed what, what's positive and negative. Each toggle switch has 2 wires soldered to the rear. Opposite, behind where the fuse sits, is a thin piece of steel with a single wire attached. Then, a wire runs up the length of the unit, this is attached to a red wire. I can get voltage readings by touching one probe of my meter on the upper of each of the soldered terminals behind the toggle switches, with the switches in the off position, the other probe on either the connections behind the fuses or the wire that runs the length of the unit. Not in the case of the toggle for the water pump though, I'm getting no readings for this (but getting 7.5 to 9 volts at the water pump, despite this switch appearing to be broken!)

 

I don't know if that makes thing clearer, or muddies them further. 

[Tony Brooks]

57 minutes ago, The Welsh Cruiser said:

I'm not quite sure but if I say there are no voltage readings from that switch, regardless of what I do or where I measure, does that answer?

I'd like to use another switch, there's one labelled bilge pump that has wires going to it but isn't used but unfortunately everything's soldered, and I don't have an iron. How might I bypass it?  

Stuff a meaty screwdriver between the two terminals but if it really is reading zero volts across the switch WITH THE MOTOR TRYING TO RUN then it is unlikely to be the switch but may well be a poor connection else where - even the pressure switch in the pump.

 

I would point out that you have not been clear as to exactly what two points you have taken your voltage measurements after the first post.

 

Unless you are testing for voltdrop (as in across the switch) one meter lead needs to go to a negative and one4 to a positive. In each case one must be known as good and the other can be to a suspect part of the circuit. So meter between a known good negative or bright metal of the hull and the positive you are trying to test. When testing for n4egative faults one lead on a known good positive like the battery positive terminal and the other on the suspect negative.

Edited September 28, 2019 by Tony Brooks

[The Welsh Cruiser]

3 minutes ago, Tony Brooks said:

Stuff a meaty screwdriver between the two terminals but if it really is reading zero volts across the switch WITH THE MOTOR TRYING TO RUN then it is unlikely to be the switch but may well be a poor connection else where - even the pressure switch in the pump.

 

I would point out that you have not been clear asd to exactly what two points you have takn your voltage measurements after the first post.

I think I've ruled out a problem with the pump by attaching it to an old battery with some wires, it ran.

 

The voltages I've quoted are either at the wire that attaches to the pump (currently varying between 7.5 and 9v) or at the switch. I'm getting no readings from the switch for the pump. The only other voltage I've quoted is the battery voltage which is currently 12.7 under slight load.

 

Could you possibly explain which terminals I could try bridging with a screwdriver?  

[Chewbacka]

38 minutes ago, The Welsh Cruiser said:

I think I've ruled out a problem with the pump by attaching it to an old battery with some wires, it ran.

 

The voltages I've quoted are either at the wire that attaches to the pump (currently varying between 7.5 and 9v) or at the switch. I'm getting no readings from the switch for the pump. The only other voltage I've quoted is the battery voltage which is currently 12.7 under slight load.

 

Could you possibly explain which terminals I could try bridging with a screwdriver?  

So the pump is ok.

The battery is ok

So there is a failure in the circuit (wiring) to the pump either in the positive (red wire supply) or the negative return (the black wires)

This type of fault finding is always best done with a volt meter, but if you are unsure lets try -

 

Turn a cold tap on and then off to ensure there is no pressure in the water system. then try  joining the 2 sides of the fuse holder together with a bit of wire (with all pump switches on).  If the pump runs it shows it is the fuse or holder that is faulty.  If you don't know what you are doing get someone to help if you can.

Edited September 28, 2019 by Chewbacka

[The Welsh Cruiser]

14 minutes ago, Chewbacka said:

So the pump is ok.

The battery is ok

So there is a failure in the circuit (wiring) to the pump either in the positive (red wire supply) or the negative return (the black wires)

This type of fault finding is always best done with a volt meter, but if you are unsure lets try -

 

Turn a cold tap on and then off to ensure there is no pressure in the water system. then try  joining the 2 sides of the fuse holder together with a bit of wire (with all pump switches on).  If the pump runs it shows it is the fuse or holder that is faulty.  If you don't know what you are doing get someone to help if you can.

Appreciate that! Unfortunately, with it being a screw cap that holds the fuse in I can't think of a way of doing that. Might there be a simple way of bypassing the switch rather than the fuse? I do have a feeling it's the switch, because when I toggled it a few times the voltage at the pump went up. Not as high as it should be, but up nonetheless. 

[Chewbacka]

2 minutes ago, The Welsh Cruiser said:

Appreciate that! Unfortunately, with it being a screw cap that holds the fuse in I can't think of a way of doing that. Might there be a simple way of bypassing the switch rather than the fuse? I do have a feeling it's the switch, because when I toggled it a few times the voltage at the pump went up. Not as high as it should be, but up nonetheless. 

Can you not get to the back of the fuse??  If so try a wire between the "red wire bringing power from the battery to the fuse" and "the red wire going from the switch to the pump". 

[The Welsh Cruiser]

4 minutes ago, Chewbacka said:

Can you not get to the back of the fuse??  If so try a wire between the "red wire bringing power from the battery to the fuse" and "the red wire going from the switch to the pump". 

Cheers I'm probably showing how little I know here! The only red wire in the vicinity is the one that connects to the wire that runs the length of the unit, close to the fuse units. All other wires are black. So, each of the 6 toggles has 2 black wires, and one black wire from its fuse.

[Chewbacka]

10 minutes ago, The Welsh Cruiser said:

Cheers I'm probably showing how little I know here! The only red wire in the vicinity is the one that connects to the wire that runs the length of the unit, close to the fuse units. All other wires are black. So, each of the 6 toggles has 2 black wires, and one black wire from its fuse.

I don't understand how your boat is wired, so it would be unwise for me to suggest anything else.  Sorry.

[ditchcrawler]

Maybe a photo of the back of the fuse panel and switch panel would help highlighting which one is for the pump

[Tony Brooks]

You really need to either follow the wires at the back of the panel and raw us a diagram or send a photo

 

If a switch has three wires on it SEPARATE TERMINALS then it is most likely an illuminated one that lights up when the switch is on so the three wires would be:

 

Live feed from the fuse or a junction box the red wire is connected to or possibly the fuse

Feed from switch to pump or possibly the fuse

Negative so bulb/LED can illuminate.

 

If the switch has three wires on two terminals so one wire on a terminal and the other two wires are on a single terminal then it is not an illuminated switch but a cheap and nasty way of wiring the positives to all the switches on the board.

 

Single wire is the switched feed to the pump or possibly the fuse

Twin wire Live feed from the fuse or a junction box the red wire is connected to or possibly the fuse

The back of the fuse holders should have two terminals on each. If one terminal on each has two wires on it then that one is the positive feed, again a cheap and nasty method of wiring. If each terminal has one wire then the fuse might be between the switch and pump.

 

The temporarily bridge the fuse just stick a length of wire or a screwdriver between the two terminals.

 

Warning - after a long life I have known glass fuses to "self-unsolder" the wire from the end cap. This can be a beast to see so substitution is the easiest way to find out if this has happened. If you have had a period of well discharged batteries this may w ell be the case.

 

13 hours ago, The Welsh Cruiser said:

I think I've ruled out a problem with the pump by attaching it to an old battery with some wires, it ran.

 

The voltages I've quoted are either at the wire that attaches to the pump (currently varying between 7.5 and 9v) or at the switch. I'm getting no readings from the switch for the pump. The only other voltage I've quoted is the battery voltage which is currently 12.7 under slight load.

 

Could you possibly explain which terminals I could try bridging with a screwdriver?  

 

1. But you have still not told us EXACTLY how you took those readings - that is EXACTLY where the meter leads were connected. Ditto the other voltages. If you just connected the meter to the two wires it proves you have a fault but no more. To go further you need to eliminate each side of the circuit in turn so:

 

Make sure your meter is properly set up to measure DC Volts. If you get it wrong you may be buying a new meter.

 

Run a length of cable from the battery negative terminal OR a bright metal part of the boat's metal structure and connect the meter between the end of that wire and the positive lead running to the pump. If you get battery voltage the  repeat with the pump reconnected and the switch on. If both tests show close to battery voltage then the positive side of the pump's circuit, including fuse and switch are OK. If you do not get two readings close to battery voltage then the fault is in the positive wiring so could eb the fuse, switch or something else.

 

Now change the length of wire to battery positive but take care, if you then tough the bare end to metal it is likely to burn you and catch fire.

 

Connect the meter between that wire and the negative cable to the pump. Expect close to battery voltage. Then reconnect the negative wire to the pump, turn the switch on and repeat the test. You should have close to battery voltage. If you do not have two good voltages the fault is between the pump and the battery negative terminal.

 

2. Explained above for fuse and switch but we need a photo or diagram to be 100% sure - I am 98% sure though..

 

It is vital we know exactly where you are connecting your meter because you could well be using two black positives and such like or trying to use paint or wood as the negative meter connection.